Bourasseau Emeric, Lachet Veronique, Desbiens Nicolas, Maillet Jean-Bernard, Teuler Jean-Marie, Ungerer Philippe
Commissariat à l'Energie Atomique, Centre DAM-Ile de France, Département de Physique Théorique et Appliquée, Bruyères-le-Châtel, 91297 Arpajon Cedex, France.
J Phys Chem B. 2008 Dec 11;112(49):15783-92. doi: 10.1021/jp8068255.
The thermodynamic behavior of the carbon dioxide + nitrogen dioxide (CO2 + NO2) mixture was investigated using a Monte Carlo molecular simulation approach. This system is a particularly challenging one because nitrogen dioxide exists as a mixture of monomers (NO2) and dimers (N2O4) under certain pressure and temperature conditions. The chemical equilibrium between N2O4 and 2NO2 and the vapor-liquid equilibrium of CO2 + NO2/N2O4 mixtures were simulated using simultaneously the reaction ensemble and the Gibbs ensemble Monte Carlo (RxMC and GEMC) methods. Rigid all atoms molecular potentials bearing point charges were proposed to model both NO2 and N2O4 species. Liquid-vapor coexistence properties of the reacting NO2/N2O4 system were first investigated. The calculated vapor pressures and coexisting densities were compared to experimental values, leading to an average deviation of 10% for vapor pressures and 6% for liquid densities. The critical region was also addressed successfully using the subcritical Monte Carlo simulation results and some appropriate scaling laws. Predictions of CO2 + NO2/N2O4 phase diagrams at 300, 313, and 330 K were then proposed. Derivative properties calculations were also performed in the reaction ensemble at constant pressure and temperature for both NO2/N2O4 and CO2 + NO2/N2O4 systems. The calculated heat capacities show a maximum in the temperature range where N2O4 dissociation occurs, in agreement with available experimental data.
采用蒙特卡罗分子模拟方法研究了二氧化碳+二氧化氮（CO₂ + NO₂）混合物的热力学行为。该系统极具挑战性，因为在特定的压力和温度条件下，二氧化氮以单体（NO₂）和二聚体（N₂O₄）的混合物形式存在。同时使用反应系综和吉布斯系综蒙特卡罗（RxMC和GEMC）方法模拟了N₂O₄与2NO₂之间的化学平衡以及CO₂ + NO₂/N₂O₄混合物的气液平衡。提出了带有点电荷的刚性全原子分子势来模拟NO₂和N₂O₄物种。首先研究了反应性NO₂/N₂O₄系统的液-气共存性质。将计算得到的蒸气压和共存密度与实验值进行比较，蒸气压的平均偏差为10%，液体密度的平均偏差为6%。还利用亚临界蒙特卡罗模拟结果和一些适当的标度律成功地处理了临界区域。随后给出了300、313和330K下CO₂ + NO₂/N₂O₄相图的预测。还在恒压和恒温条件下的反应系综中对NO₂/N₂O₄和CO₂ + NO₂/N₂O₄系统进行了导数性质计算。计算得到的热容在N₂O₄发生解离的温度范围内出现最大值，这与现有实验数据一致。
